Semiautomatic hydraulic-electric gun charger



April 20, 1948. J. M. BOSHKA ETAL SEMIAUTOMATIC HYDRAULIC-ELECTRIC GUN I iled March 15, 1945 CHARGER 2 Sheets-Sheet 1 April 20, 1948. J. M. BOSHKA EI'AL SEMIAUTOMATIC HYDRAULIC-ELECTRIC GUN CHARGER .Filed March 15, 1945 2 Sheets-Sheet 2 s v R 6 W55 y mwfz E 0@ N M e A w MGM? A u m \\\\\\\\\\\k E Nm W %N Patented Apr. 20, 1948 SEMIAUTOMATIC HYDRAULIC-ELECTRIC GUN CHARGER Joseph M. Boshka, George A. Goepfrich, and

Frank V. Kuzmitz, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application March 15, 1945, Serial No. 582,824

This invention relates to aircraft armament and is particularly concerned with the provision of apparatus for charging machine guns.

Most present-day types of military aircraft are equipped with one or more machine guns located in the wings or in the fuselage at points which are generally remote from the pilot or gunner. In most instances, the guns are provided with trigger means located near the control stick of the aircraft for actuating a firing solenoid attached to the guns.

To initiate firing of such amachine gun after a new belt of ammunition is supplied a reciprocable bolt stud is provided which must be pulled rearwardly and released for counter-movement to feed the first cartridge from the ammunition belt into the gun. After the first cartridge has been fed into the gun and fired the gun will automatically eject the used cartridge and feed another one into the gun chamber. However, the insertion of defective ammunition into the gun chamber results in a misfire of the gun which interrupts normal gun operation. This defective cartridge may be removed by manually operating the bolt stud to extract the defective cartridge and then feeding a new one into the gun chamher. After this manual operation of the gun bolt stud the gun is now ready for firing. Since most guns are so remotely located in the aircraft, manual charging is not only very diflicult but impractical. It is to cope with this cumbersome method of manual charging that the present invention incorporating semi-automatic means to simulate normal gun operation has been proposed.

It is, therefore, an object of this invention to provide a semi-automatic mechanism for charging a gun.

A further object of the invention resides in the provision of a semi-automatic gun charging mechanism which is constructed and arranged to complete a charging cycle once initiated.

Another object of the invention is to provide a gun charging mechanism having manual means for controlling a charging cycle.

An important object of this invention is to provide means responsive to predetermined pressures for operating the charging mechanism.

A further important object resides in the provision of a pressure-operated device which is constructed and arranged to connect the charging mechanism for exhausting the pressure acting therein when it exceeds a predetermined low value.

An additional object of the invention is to pro- 16 Claims. (Cl. 89-1) vide a pressure-operated charging motor in combination with an electrical system which responds to predetermined pressures acting in the motor for retracting the bolt stud of a gun and then releasing the stud for countermovement.

A still further object of the invention is to provide a fluid pressure system for a charging mechanism having means for exhausting the fluid under pressure should it exceed a predetermined maximum value. 7

Other objects and advantages of thepresent invention should be readily apparent by referring to the following specification, considered in conjunction with the accompanying drawing which is illustrative of one embodiment thereof, but it will be understood that any modifications may be made in the specific structural details thereof within the scope of the appended claims without departing from or exceeding the spirit of the invention.

Figure 1 shows the invention in diagrammatic form with parts in section; 7

Figure 2 is a detailed plan view of the charging device of the invention, showing portions broken away and in section;

Figure 3 is an elevational view in detail of the latching mechanism of the charging device showing the auxiliary piston in latched position;

Figure 4 is a plan view of a part of the latching mechanism;

Figure 5 is a section taken on the line 55 of Figure 4; and

Figure 6 is a section through v the inlet connection.

Referring to Figure 1 of the drawing, reference numeral l0 designates a reservoir which contains an adequate supply of fluid to be put under pressure in an accumulator 20 by a pump '25. Disposed between the pump and accumulator is a regulator or unloading valve 30, of any conventional design for disconnecting the accumulator from the pump to by-pass the fluid to the reservoir when the fluid in the accumulator has been put under a predetermined maximum'pressure and for connecting the accumulator to the pump to charge said accumulator when the fluid under pressure in theaccumulator" has fallen to a predetermined minimum value. The accumulator 20 is connected to one or more charging devices 32 which are mounted on guns 34 to chargethe same when desired. The charging device or hydraulic motor per se, which'will be subsequently described in detail, is constructed and arranged to engage a bolt stud- 38 for reciprocating it to charge the gun in the event of its malfunction.

mally closed valve 42. The valves 40 and 42 are of the electrically operated type.

A pair of pressure-responsivedevices or pres sure switches 44 and 46 are constructed and arranged to respond to predetermined maximum.

The charging motor 32 is held in operative re lationship to the gun by brackets 16 and I2 which are secured to the gun frame. The charging motor per se comprises a cylinder 14 having a slotted portion I6 which extends longitudinally thereof. 'One end of the cylinder is threaded internally at I8 to receive afittihg 8E1 equipped with an inlet connection 82 for connecting the motor to the hydraulic source.

"the cylinder is apiston 84 comprising an outer Disposed within 'T'tube 8fi, an inner tube 88 and an extended shank and minimum pressures respectively acting in the charging motor. 11; istolhe noted thatjthis; combination of pressure switches may be used with a single charging motor or,with.a plurality of charging motors comprising a si'ng'le group, as shown in the drawing.

To prevent destruction of the mechanism due to thermal expansion of the fluid, under certain conditions of operation whenthe exhaustval'vie isrendered inoperative a thermal relief valve 48'i's disposed between the charg gmec amsmam the reservoir, tendency for'abno'r'mall'y' high and hazardous pressures' 'to' act on the mechanism will operate the relief valve to cause the fluid to be bleddireqtly to the res'ervoir whereby that pressure above the predetermined maximum pressure acting on the mechanisrnjis relieved'.

An electrical system is provide d forfco'ntrolling valves 4Il and 42. The electricai system may be n n ent y di d d. a firslia'nd afi'e'con'd circuit. The first circuit is connected to a source 50 and to a windingfifl a of -the valve 49 The circuit nclude a dp bls qle ilbl fih fw Switch 52, a nual y o rated,pusa utt e i h 4. normally open with respect tofthe first circuit, the normally closed high pressureswitch 44, a relay 56, and a holding circuit having connecn 55. we, piinep ed Pa al with. the switch 54. The holding circuitl'whiich is "normauy o en ncl des mon a e: 5? whiqh s c os h he lay rcom i .611 en r i es ns sponse to closing switch 54; onto contacts 54d and 2- W he. wi snfit s eleased, it sthe orma l QWIIPQSWWKR ew in the drawin lwi h re pect thefi s 'f l i j on r 3. ie u ha f l ssd .9 completes the circuit to maintain the relay. 55 energized and to supply current to the windin 50a to operate the valve 40 to admit fiuid under pressure to thQcharging mechanism. The c'ontactors 58 and 6B are in the form o f a double pole knife switch and in conjunction with relay coil 56 provide acontrol device forthe holding circuit andthe second circuit. V V

The second circuit connectslthe source "5 to a winding 42a of the valve 42 andcomprises the double poledouble throw switch 2 the switch 4. normally c edwithrespe 9 he s l d circuit on contacts 54eand 54d," the normally en w-press re wit h] .6.. d. ommit 6O whichnorrnally closes the secpn d circuitbjut is ned en. he e ayifi i ergi e l-f he switch 52 s nstr ted-and a n ed o be closed on either co ntacts 52a. and 520 orcontact 2b to onn t-.tha narei s ghe ism t at y os ion or aiet i ps i qn tr srse r w- That is, if it] is desiredtor complete a charging ycle e w cn isjmpred 9 v. =-v i -"r; s ie so that. the.v ol wi l .be. tra ted arid. h n. leased for counterrnovernent. However, if it is desired-to retract thebolt andj-holdfitin re: tracted position to prevent unintentional .firin'g.

of the gun the switch is movedto' safety position.

portion 98. The fitting is drilled at 92 to slidably. rec'eivelthe shank portion 96. A close machine tolerance. is held between the drilled 5'poit'ion'MCahdfthe shank so as to provide a dash-pet 'efict upon the piston to retard its motionhttlie' endof the return stroke as shown in Figure 2 The piston is returned to this latter position by a spring 94.

Disposed in the other end of the cylinder I4 from the inlet 82 is a latching mechanism comprising a retainer plug 96 longitudinally bored at S'Ial'id havi'n'g'ala'rge diameter 98 and a small diameter IQQJ The-[large diameter is drilled at I92 for the receptioniofa bolt IM to secure the plugto'the cylinder'lfi'. The enlargeddiameter of the retainer'plug 96 is further drilledtransversely at Iilfiand I88 t o receive pins III! upon which latching levers or dogs 'II2 are pivotally mounted. The plug 96 is slotted'at II4 to allow the dogs II2 to expand or pivot about the pins III) A guide sleeve" I I5 has one end secured in the bore 91 by a pin H8. An actuating member IZIlengages the latching levers II2 to pivot the same about pins H ll. The member isslidable within the sleeve Ii'fi and is provided 'withan extension rod I22 havingan enlargedend I24. The pm I I8 acts as a stop forthe actuating member I20 and also keeps the levers I I2 spaced apart when the member is in its normal position. The inner tube 8 8fhas fixed thereto an expanded head member I26 drilled at I21 to slidably receive' the rod I22. An auxiliary piston or bolt engaging -member I28 is freely reciprocablewlthin the cylinder I5 and is provided with a lug I30 forengagingthe bolt stud or slide 38 of the gun when it is desired to move the bolt to the rear tosirnulate normal gun operation. The lug I30 protrudes through the longitudinally slotted portion I5 provided therefor. The dogs "I I2 are providecl 'with inclined surfaces II3 for cooperat ing with inclined surfaces I29 of the auxiliary piston I23 whenthe piston has been moved to the position shown in Figure 3,'for latching the bolt 38 to the rear.

The admission of fluid under pressure at the inlet 82 causes piston 84 and itsasso'ciated parts 86 and 83 to move to the left. The tubeBG engages the auxiliarypiston lfl and carries .it to the'lef t to the position shown in Figurefi, The head member I26 which is fixed to the tube 88 is likewise carried to the left to engage theactuatingmeniber I20 to cause the same to move be: tween the dogs I I 2 tothereby expand said dog s so that the inclinedsurfaces I.I3'and I29 coact to latch the auxiliary piston and bolt stud to the rear. Afterflatching of thebolt to the rear has beencohsumrnated fiuid under pressure in the charging motprisexhausted and the p-iston 84 returns to the position'shown in Figure 2, under the action oi sprir' ig'fifi, Because of tl le lostmo- 'o connection between the head member 126 of piston 84'and the actuating member I2Il thehead member I26 does not engage theenlargedend I24 of the actuating memberuntil the piston 84 has approached the end of its return stroke- Engagement of the end I24 by the head I26 moves the member I20 from between the latching levers II2. Now the levers are free to swing inwardly. The force of the spring returned gun bolt acting against'the lug I30 tending to return the auxiliary piston to its forward position will be transmitted to the inclined surfaces I29 to thereby create a camming action between the two surfaces II3 and I29 to causethe latching levers to be rotated out of engagement with the auxiliary :piston. This arrangement whereby the bolt stud is not released until the piston 84 has approached the end of its forward or return stroke permits the unimpeded return of the bolt stud. It is to be noted that the organization of the parts and the timing is such that when the bolt is moved rearwardly the auxiliary piston must move over the dogs before the actuating member is moved between the dogs so that when the dogs are expanded their inclined surfaces I I3 will engage the inclined surfaces I29 of the auxiliary piston.

Operation of the charging mechanism is as follows: Assume the switch 52 is in battery position, that is, closed on contacts 52a and 520, and it is desired to charge the guns 32. Here it will be well to bear in mind that when the double pole double throw switch 52 is closed on battery position, the first circuit is open through the manually controlled switch 54, which is normally open with respect to the first circuit and that the second circuit is open through the normally opened low pressure switch 46. The holding circuit, which is a part of the first circuit, is open through the contactor 58. Therefore the normally closed valves 40 and 42 are closed since the respective windings 40a and 42a are not energized so as to cause the valves to be operated.

To charge the guns, the manually controlled switch 54 is closed on contacts 54a and 54b. This energizes winding 40a and operates valve 44 to admit fluid pressure to the charging mechanism. Relay 56 which was also energized upon the closing of switch 54, as above described, closed contactor 58 which completed the holding circuit to thereby provide a secondary current path to the valve 40 and relay 56. This secondary path provides for the completion of a retracting operation of the bolt once the cycle is initiated notwithstanding manually-operated switch 54 has again been allowed to resume its normal open positiion with respect to the first circuit. In this latter position of the switch it is normally closed with respect to the second circuit. Fluid under pressure will now be admitted past valve 40 to the charging mechanism until the pressure in the mechanism has reached a predetermined maximum value, at which time the normally closed switch 44 will open the first circuit to deenergize the winding 40a to allow valve 46 to close to cut off fluid under pressure to the charging mechanism. Opening pressure switch 44 also deenergizes relay 56 which opens contactor 58 to break the holding circuit including connections and 51, which as aforementioned, comprise a part of the first circuit.

It will be remembered that pressure switch 46 which is normally open tends to close the second circuit in response to predetermined low pressures in the charging mechanism. Consequently, after valve 40 is opened and the pressure rises above a fixed low value in the charging mechanism switch 46 closes. However, whether the second circuit will now be closed to pass current to the winding 42a to operate valve 42 depends upon the pres-' sure in the charging mechanism. If the switch 44 has opened in response to high pressure in the charging mechanism to open the first circuit to deenergize relay 56 to thereby allow the normally closed contactor 60 to close, the second circuit will be closed. With the low pressure switch 415 closed and contactor 60 in its normally closed position, after relay 56 is deenergized, current passes through the winding 42a to energize it to operate valve 42 to exhaust fluid under pressure from the charging mechanism to complete the charging cycle. When the pressure in the charging mechanism has been exhausted to a predetermined low value switch 46 will open the second circuit which deenergizes winding 42a of valve 42 to allow it to resume a normally closed position.

It is well known that fluids of the type used in hydraulic systems change in'volume due to temperature variations. When such a fluid is confined to a prescribed space, such as in the charging mechanism of the present invention, expan-v sion of the liquid may cause unintended movement of some associated part of the mechanism, in this case the bolt stud. To preclude such undesirable action, pressure switch 46 is constructed and arranged to close the second circuit upon a rise in pressure in the charging mechanism above a predetermined value. This will energize winding 42a and cause valve 42 to be operated to ex haust the pressure from the charger.. The foregoing action takes place so long as the single pole double throw switch is in battery position. However, with the switch in safety position the second circuit which controls exhaust valve 42 is no longer capable of energizing winding 42a so other means must be provided for exhausting the fiuid pressure in the charger mechanism which may be caused by thermal expansion of the fluid.

To safety the guns, switch 52 is moved to safety position. This causes valve 40to be operated to admit fiuid under pressure to the mechanism to build up the pressure therein until it reaches a predetermined maximum value at which time switch 44 opens to deenergize the valve 40 to cut off the source of fluid under pressure.

After the operation just described fluid pressure at its maximum value is confined in the chargingmechanism. In order to properly protect the mechanism from injury due to excess pressure rise, caused by thermal expansion of the fiuid, when the guns are in the safety position, means such as the relief valve 48 is provided for discharging fluid pressures in excess of a predetermined value. This valve is so constituted that the excess fluid under increased pressure will be by-passed directly to reservoir when thepressure rises above a predetermined value.

We claim: I

1. The combination with a machine gun having a bolt stud reciprocable during normal gun operation, of a hydraulic system comprising a charging device for retracting the bolt stud and then releasing the same for 'countermovement, a source of fiuid under pressure connected to the charging device, means operable for controlling the flow of said fluid under pressure to the charging device, means operable for exhausting said fluid in said charging device, and means for controlling a charging cycle including a pair of devices responsive to predetermined high and low pressures respectively acting in said charging device, said high pressure device constructed and arranged to control said first-named means, said low pressure device constructed and arranged tocontrol said second-named means holding circuit constructed and arranged to close in response to energization of said control device to provide another path for current to said control device to keep the same energized after opening said first switch to enable the completion of a bolt retracting movement once initiated.

8. A mechanism to be associated with a machine gun for retracting the bolt stud thereof and then releasing it for countermovement comprising a charging motor having a portion engageable with the bolt stud, means operable for admitting fluid under pressure to said motor, means operable for exhausting said fluid under pressure, a first circuit including said first-named means and a control device, a first switch in the first circuit to close the circuit to operate said first-named means to admit fluid under pressure to the motor and to energize the control device, means in the first circuit responsive to a predetermined high pressure in the charging motor to open said first circuit to render said firstnamed means inoperative and to deenergize said control device, a second circuit including said second-named means, said control device comprising a double pole switch constructed and arranged so that one pole is in the second circuit normally closed but openable in response to energization of said control device, whereby opening the first circuit permits said double pole switch to close said one pole thereof to operatesaid second-named means to allow fluid under pressure to be exhausted from said motor, and means in the second circuit responsive to a predetermined low pressure in the charging motor to open said circuit to disconnect said second-named means therefrom, said first circuit including a holding circuit constructed and arranged to close in response to energization of said control device to provide another path for current to said control device to keep the same energized upon opening said first switch to thereby complete a bolt retracting movement once initiated, said other pole of said double pole switch constructed and arranged in the holding circuit to be normally open and closable in response to energization of said control device.

9. A mechanism to be associated with a machine gun for retracting the bolt stud thereof and then releasing it for countermovement comprising a charging motor having a portion engageable with the bolt stud, means operable for admitting fluid under pressure to said motor, means operable for exhausting said fluid under pressure, a first circuit including said first-named means, a switch in the circuit for closing the same to operate said first-named means to admit fluid under pressure to the motor, means in the first circuit responsive to a predetermined high pressure in the charging motor to open said first circuit to disconnect said first-named means from said circuit, a second circuit including said second-named means, means in the second circuit responsive to pressure above a predetermined low pressure in the charging motor to close said second circuit to operate said second-named means to exhaust fluid under pressure from said motor, and means in the first and second circuits responsive to closing the first circuit to open the second circuit to render said secondnamed means inoperable.

10. The combination with a machine gun hav-- ing a bolt stud reciprocable during normal gun operation, of a pressure operated charging motor for operating the bolt stud, means for admitting fluid under pressure to said charging mo- 10 tor, means for exhausting said fluid under pressure from the charging motor, means comprising a pair of devices responsive to predetermined high and low pressures acting in said motor for controlling respectively said first and secondnamed means, said last-named means comprising an electrical system including said first and second-named means, said first-named means constructed and arranged in said system to be controlled by said high pressure device responsive to predetermined high pressure in the charging motor to shut on? the flow of fluid under pressure to said motor, said second named means constructed and arranged in said system to be controlled by said low pressure device responsive to predetermined low pressure in the charging motor and by electrical meansin said electrical system, said electrical means constructed and arranged to be controlled bysaid high pressure device whereby fluid under pressure is exhausted from said charging motor, and manual means in said electrical system for controlling a charging cycle.

11. In combination with a machine gun having a bolt stud reciprocable during gun operation,

a charging device associated with the gun for reciprocating the bolt stud to charge the gun, a first means operable for admitting fluid under pressure to saiddevice,a, second means operable for exhausting said" fluid under pressure from said device, an electrical system, comprising a first circuit includingsaid first means and a pressure switch normally closed but constructed and arranged to be opened when the pressure in said device reaches a predetermined maximum value to allow said first means to shut off said fluid under pressure, a second circuit constructed and arranged tobe olosedafter said first circuit is opened and including said second means, and manually operated means for controlling a charging cycle and constructed and arranged to open the second circuit to disconnect said second means therefrom and close the first circuit, to operate said first means to admit fluid under pressure to said device.

12. In combination with a machine gun having a bolt stud reciprocable during gun operation, a charging device associated with the gun for reciprocating the bolt stud to charge the gun, a first means operable for admitting fluid under pressure to said device, a second means operable for exhausting said fiuid under pressure from said device, an electrical system, comprising a first circuit including said first means and a pressure switch normally closed but constructed and arranged to open when the pressure in said device is above a predetermined maximum value to disconnect said first means from the first circuit to allow said first means to shut oii said fluid under pressure, a second circuit including said second means and a pressure switch normally open to disconnect said second means from the second circuit but constructed and arranged to be closed when the pressure in said device is above a. predetermined minimum value, and manually operated means movable from a normal p0- sitlon closing. said second circuit to a position of closing the first circuit and opening the second circuit to operate said first means to admit fluid under pressure to said device whereupon said manually operated means is allowed to resume its normal position to operate said second means.

13. In combination with a machine gun having a bolt reciprocable during gun operation, a charging device associated with the gun for reciprocating the bolt to charge the gun, a first auamom means operable for admitting: fluid-ninderpressure to said device, a second means operable for exhausting said fluid under "pressure from said device, anjelectricai system, comprising a first circuit including said first means and a pressure switch normally closed t-o render said first means operable to admit fluid "under pressure to :said device but constructediand' arranged to be opened when the pressure in said-device reaches :a predetermined maximum value to render-:said-first means inoperable to therebypshut' off said .fluid under pressure, .a relay :in the first circuit, a second circuit including :saidwsecond means ands pressure switch normally open to disconnect said second means from said second :circui-t but con structed and arranged to 'be closed when the pressure in said device isabove a predetermined minimum value, said relay including-'mea-n's-m the second circuit responsive to energization'of the relay for keeping- ;said :secondcircuitopen when the first circuit is -clos'edto render said second means inoperable when said first means is operated, and manually: operated means'in'the first and second circuits for controlling charging of the-gun.

14. In combination with -;a machine gun having a bolt reciprocable during gun operation, a charging device associated with the gun for reciprocating the bolt to charge the gun, e, firstmean-s operable for admitting fluid-under pressure to said device, a second means operable for exhaustin said fluid underpressure from said device, an electrical system, comprising afirstcircu-it including said first means and .a pressure switch normally closed to render said first means operable to admit fiuid under pressure to said devicebut constructed and arranged to be opened when the pressure insaid device reaches: a, predetermined maximum value to render said first. means inoperable to thereby shut off said-fluid under pressure, a relay in the first circuit,- a second circuit including said second means and a pressure switch normally open to disconnect said second means from said second circuit but oonstructed and arranged to be closed when-the pressurein said device reaches a predetermined minimum value, said' relayincluding means: in the second circuit responsive to energization of the relay'for keeping said second circuit open when the first circuit is closed, and manually operated means in the first and second circuits for controlling charging of the gun, said first circuit including a holding'circuit normally open but constructed and arranged to be closed by said relay when said first circuit is closed by said manually operated means, said holding circuit constituted to remain closed when the first circuit-isopenedbythe manually operated means to thereby complete a. charging cycle once initiated.

15. In combination with a machine gun having a bolt reciprocable during gun operation, a. charg ing device associated with the gun for reciprocating the bolt to charge the gun, afirst means operable for admitting fluid under pressure to said device, a second means operable for exhausting said fluid under pressure from said de- I2 vice, an electrical system, comprising a first circuit'including said first means and a pressure switch normally, closed but constructed and arranged to open when the pressure said device is above .-a predetermined maximum value, a second circuit-including said second means and a pressure switch normally open but constructed and arranged to be closed when the pressure in said device is above a predetermined minimum value, manually operated meansmovable from a normal position closing said second circuit to a position of closing the first circuit and opening thesecond circuit to operate said first means to admit fluid under pressure to said device whereupon said manually operated means is allowed to resume its normal position, a two-position switch disposed'in the electrical system ahead of said manually operated means and constructed and arranged in the first and second circuits to have a first position which energizes said circuits through said manually operated means anda second or safety position which energizes only said first circuit through .ashunt around said manually operated means, and means responsive to pres" sure-in the char-gingdevice to release only the pressure therein above a predetermined value whereby-the bolt stud is held a preselected position when the two-position switch is in the second position 16. A mechanism for-use with a machine gun having a. bolt stud which is to be retracted and released forcountermovement when charging the gun is desired comprising a fiuid system having afiuid'motor therein adapted to engage the bolt stud, electrical means including a device operable for admitting'fluid under pressure to said system, a device operable for exhausting said fiuid under pressure, a switch constituted to have one position for energizing said first named device for operating the same to admit fluid under pressure into said-system and a second position for energizing said second named device for operating the same to exhaust said fluid under pressure, and means responsive-to predetermined high and low pressures in said fluid system for respectively deenergizing said first named device and energizing said second named device.

JOSEPH M. BOSHKA.

GEORGE A. GOEPFRICH.

FRANK V. KUZMITZ.

REFERENCE S CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 2,115,483 Defives Apr. 23, 1938 2,116,860 Blaylock et a1 May 10, 1938 2,332,419 White et a1 Oct. 19, 1943 2,355,179 Pontius Aug. 8, 1944 2,356,981 Drescher et a1 Aug. 29, 1944 FOREIGN PATENTS Number Country Date 4581,313 Great Britain Mar. 9, 1938 Certificate of Correction Patent No. 2,440,071. April 20, 1948. JGSEPH M. BOSHKA ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 45, strike out the word under and insert the same after fluid, line 37, same column; column 8, line 8, claim 5, strike out the Words open said first circuit to and insert the same before render, line 7, same claim; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 14th day of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,440,071. April 20, 1948.

JOSEPH M. BOSHKA ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requlnng correctlon as follows:

Column 6, line 45, strike out the word "under and insert the same after fluid, line 37, same column; column 8, line 8, claim 5, strike out the Words open said first circuit to and insert the same before render, line 7, same claim;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 14th day of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

